1. Field of the Invention
This invention relates to polyurethane foam surfactants. More specifically, this invention relates to novel surfactants made from polydialkylsiloxane-polyoxyalkylene copolymers which have both hydrocarbon and hydroxy capped polyoxylalkylene pendants on the same copolymer. These surfactants have particular advantage in manufacturing flexible polyurethane foam with higher than normal amounts of solid polymer.
2. Prior Art
Molded, flexible polyurethane foams are produced by the reaction of high molecular weight polyols, which polyols have greater than 40% of primary hydroxyl capping, with organic isocyanates and water. Molded, flexible polyurethane foams are distinguishable, in part, from conventional hot cure polyurethane foams by the use of such a high percentage of primary hydroxyl groups as well as by the fact that molded flexible polyurethane foams require little or no oven curing and thus are often referred to as cold cure foams. Such foams are extremely desirable for cushioning applications because of their excellent physical properties, e.g., very high foam resiliency, open celled structure, low flex fatique, i.e., long life, and high SAC factors, i.e., load bearing properties.
Because of the high reactivity of molded, flexible foam ingredients and their rapid buildup of gel strength, sometimes the foam can be obtained without a cell stabilizer. However, such foams typically have very irregular, coarse cell structure as particularly evidenced by surface voids. A variety of attempts have been made to solve this problem through the use of stabilizers consisting of substituted polydimethyl- or polyphenylmethyl-siloxanes.
One group of stabilizers, described in U.S. Pat. Nos. 3,741,917 to Morehouse et al and 4,031,044 to Joslyn et al., is based on polydimethylsiloxane-polyoxyalkylene copolymers. The polyoxyalkylene pendant groups on the stabilizers in these patents, however, are always hydrocarbon capped.
Other polysiloxanes bearing pendant groups have also been claimed as stabilizers for molded flexible urethane foam. In general they are copolymers consisting of a polydimethylsiloxane to which are attached organic pendant groups that include: methyl groups (U.S. Pat. No. 2,901,445); cyanoalkyl groups (U.S. Pat. No. 3,905,924); phenylethyl groups (U.S. Pat. No. 3,839,384); alkyl groups (U.S. Pat. No. 4,306,035); trimethylsiloxy groups (U.S. Pat. No. 3,844,847); sulfolanyloxyalkyl groups (U.S. Pat. No. 4,110,272); morpholinoalkoxyalkyl groups (U.S. Pat. No. 4,067,828), and the tertiary hydroxyalkyl group (U.S. Pat. No. 4,039,490). None of these patents suggest hydroxy terminated polyoxyalkylene pendant groups attached to the siloxane chain let alone a copolymer with a mixture of both hydroxy and hydrocarbon terminated pendants on the same copolymer.
Recent U.S. Pat. No. 4,478,957 to Klietsch et al does describe polysiloxane-polyoxyalkylene copolymers wherein the polyoxyalkylene portions of the copolymer are either totally hydroxy terminated or totally alkyl, carboxy, or alkylaryl capped. Again, however, this patent does not contemplate using a single copolymer which has both hydroxy terminated and hydrocarbon terminated polyoxyalkylene pendants attached to it. Nor does the patent contemplate the use of hydroxy capped pendants when the copolymer might be used in a blend with another copolymer.
Moreover, all of the above mentioned stabilizers have been designed for molded flexible polyurethane foam containing low levels of reinforcing grafted copolymer rather than those containing high concentrations of these solids. This distinction is important for reasons discussed below.
Reinforcing grafted copolymer polyols are typically prepared by polymerizing one or more ethylenically unsaturated monomers, for example styrene and acrylonitrile, in a polyether polyol, or by reacting a diisocyanates with polyamines or hydrazines in a polyether polyol. Typically, the reinforcing grafted copolymer polyols for current molded polyurethane formulations contain about 20 percent solids in the polyol. This is normally formulated as about 50 percent of the final grafted copolymer content, thus bringing the actual solids content to about 10 percent.
Recently, however, it has become desirable to manufacture molded, flexible foam with increased firmness. Increased firmness is desirable so that thinner or lower density foam sections can be manufactured with load bearing properties equal to sections currently being made, or for the manufacture of sections with greater firmness where higher load bearing foam is desired. Such improved foams are especially desirable in the automotive seat market where reduced size and weight are important considerations in the design of smaller automobiles. One important method of achieving greater foam firmness is to increase the concentration of solids used in the urethane formulation.
Most recently, blends of conventional flexible polyurethane foam surfactants and high resiliency polyurethane foam surfactants (U.S. Pat. Nos. 4,309,508 and 4,477,601) have been taught as a method of increasing the concentration of these solids in the total polyol mixture. The small amounts of a conventional surfactant required presents considerable difficulties as minor errors in preparing these stabilizers can have significant, adverse effects on the performance characteristics of foam stability or foam breathability. Also, as in those systems for stabilizing low levels of reinforcing grafted copolymer solids, hydroxy groups are not present as the capping group in the pendant chain of these copolymers.
Of further concern in selecting a stabilizer is the breathability or open celled character of foam. Greater breathability, i.e., more open celled character, of the foam is desirable because it provides a greater processing latitude. A narrow processing latitude forces the foamer to adhere to very close tolerances in metering out the foaming ingredients which can not always be accomplished. Further, greater breathability provides foam that is considerably more easy to crush, thus avoiding splits that might occur during crushing. This characteristic is particularly desirable in foamed parts that incorporate wire inserts which are difficult to crush.
This invention provides stabilizers that are capable of providing foam stability for the desired higher levels of reinforcing grafted copolymer solids in high resiliency molded polyurethane foam. This invention also provides stabilizers that meet the above criteria and provide high breathability foams. A method is provided for preparing these stabilizers. A method is further provided for meeting the stability and breathability requirements of particular firm foam formulations over a wide range of reinforcing grafted copolymer concentrations.
Objectives
It is thus an object of this invention to provide increased foam stabilization and foam breathability by utilizing a single polydialkylsiloxane-polyoxyalkylene copolymer having two or more polyoxyalkylene pendants capped at least one of which is capped with a hydroxy group and at least one of which is capped with either an alkyl group or with an acyl group.
Another object of this invention is to provide a process for making an improved open celled, i.e., high breathability, polyurethane foam from the copolymer described.
It is a still further object of this invention to provide surfactants which can be used in manufacturing foam with higher than normal amounts of solid polymer.
It is yet another object of this invention to provide foams having fewer surface voids.
It is still another object of this invention to provide a process for manufacturing foam utilizing broad processing latitude.
Other objects and advantages of the invention will become apparent as the description thereof proceeds.